Efficient pretreatment and utilization of C-lignin from castor shells

C-lignin is a linear aromatic biopolymer with a uniform structure and acid resistance formed by catechol monomers linked through unique benzodioxane bonds. Compared to the heterogeneous guaiacyl (G)/syringyl (S)-lignin, the homogeneous nature of C-lignin enables its efficient depolymerization into a single catechol product, making it more suitable for downstream processing. This study investigated effects of various Brønsted acids and Lewis acids in a dimethyl isosorbide (DMI) /H 2 O co-solvent system on the C-lignin extraction from castor shells. Results show H 2 SO 4 assisted DMI/H 2 O co-solvent enables the most efficient disassembly of C-lignin containing sample with a yield of 95 mg/g castor shells. Quantitative 13 C NMR analysis indicates that the molar concentration of caffeyl alcohol units in the lignin is 2.06 μmol/mg, corresponding to 34.2 % C-lignin by weight at 120 °C within 2 h. The obtained C-lignin can be selectively converted to catechol derivatives (yield: 89 mol%) via Pd/C catalysis. This study demonstrates efficient pretreatment and utilization of C-lignin, offering a promising potential approach for its industrial uses.